CM3511 Datasheet, PDF (1/13 Pages) California Micro Devices Corp – Dual USB Overcurrent Switch 1.2A (VCC) / 200mA (VSBY)

CALIFORNIA MICRO DEVICES
PRELIMINARY
CM3511
Dual USB Overcurrent Switch 1.2A (V_CC) / 200mA (V_SBY)
Features
• Dual outputs, each with independent over-current
protection circuitry and indicator
• Supports standby mode in PCs so that a peripheral
can ramp down safely to a current <100mA
• Up to 1.2A (V_CC) / 200mA (V_SBY) continuous
current on each output
• Over-current limits at 1.2A / 200mA respectively
• 10msec min fault blanking delay on OC# outputs
prevents false overcurrent alarms
• Prevents backdrive current when host powered off
• Low operating current (95µA typ.)
• Small 8-Lead SOIC package
Applications
• PC motherboards, Notebooks, Set-Top-Boxes
The CM3511 also prevents backdrive current
flowing into the host from the connected peripheral.
This can occur when V_CC is removed as the host
powers down, and the peripheral still has normal
power applied. The 5V from the peripheral can
therefore be linked to the host’s V_BUS, potentially
causing backdrive current into the host and
overloading the peripheral power supply.
Pin Diagram ^GND
V_CC
V_SBY
SEL
TOP
SOIC-8
OC1#
V_OUT1
V_OUT2
OC2#
Product Description
California Micro Devices’ CM3511 is a dual port
USB overcurrent power switch that selects between
two independent 5V inputs available on a PC,
depending on the state of a logic input (SEL). The
device has two pairs of power switches, and each
pair is an analog “OR” function, providing a
continuous voltage at both outputs during power
transfer between inputs.
V_CC is the main 5V supply, which can be disabled in
a PC, and V_SBY is the 5V standby supply which is
powered up whenever the PC has power. When the
‘SEL’ pin is at logic high, V_CC is the assigned input
power supply. When ‘SEL’ is at logic low, V_SBY is
used to power the output, and no current is taken
from V_CC. Both switches can be deselected and
switched off by not driving (floating) the ‘SEL’ input,
which places the chip in low power mode.
Both pairs of switches have over-current protection.
Depending on whether ‘SEL’ is high or low, a current
over 1.2A or 200mA respectively out of either output
causes the device to enter a constant-current mode,
where the output voltage is progressively reduced to
prevent the current from increasing further. Each
output is independent of the other, so if one of the
switches is switched on but is not in overcurrent
mode then it will remain switched on. The OC#
output becomes active only if the overcurrent
condition exceeds a minimum continuous duration of
10ms.
If the overcurrent condition is severe enough that
the part heats up to the thermal limit T_MAX, the switch
turns off and the temperature cools down to T_MIN.
The switch then turns on again, and the device
heats up again, and so on, until the fault is removed.
Typical Application Circuit
5V V_CC
5V V_SBY
Select V_CC
GND
V_CC
V_SBY
SEL
OC1#
V_OUT1
V_OUT2
OC2#
V_BUS
V_BUS
Simplified Electrical Schematic
V_CC
SEL
V_SBY
CP
CP
H Over
current
protect
L Over
current
protect
H Over
current
protect
L Over
current
protect
2 USB Ports
2 USB Ports
OC1#
V_OUT1
OC2#
V_OUT2
© 2002 California Micro Devices Corp. All rights reserved.
11/10/03 430 N. McCarthy Blvd, Milpitas, California 95035
Tel: [phone]
Fax: [phone]
www.calmicro.com
C0970500
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